Possible false positives when using an ignition interlock device

Recently I had a review hearing where a client was accused of a false positive on the ignition interlock device. Over the years as a DUI lawyer I have heard many stories about the cause of false positives from ignition interlock devices. The stories range from the believable to the impossible. Here are a few reasonable explanations that can cause a false positive from an ignition interlock device.

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Spicy foods. In some cases spicy foods, when mixed with the HCl in the stomach creates a gas called methane. This methane gas will create a false positive because the sensor reacts to the hydrocarbons and thinks it alcohol.

Chewing tobacco. Many brands of chewing tobacco contain raw ethyl alcohol. Ethyl alcohol is the same type of alcohol that is found in alcoholic beverages like wine, beer and hard liquor. Ethyl alcohol is also the type of alcohol that breath testing machines are programmed to detect.

Mouthwash/Mouthspray. Mouthwash and sprays usually contain up to 30% alcohol and will definitely react as alcohol in all ignition interlock devices. Non-alcohol mouthwash is available and all ignition interlock users should use this mouthwash. The alcohol concentration level can register as high as 0.25% but typically dissipates within 15 minutes or so.

Sweets like cookies and donuts. The sugar and the active yeast can combine to create a low level alcohol fail some of the time.

Energy drinks. Many energy drinks contain low concentrations of ethanol. In fact a recent study to determine the extent of reaction of the energy drinks found positive test results on an ignition interlock device were given by 11 of 27 beverages (40.7%) energy drinks tested. That is almost half.

If you have been charged with a DUI in Seattle or any other city or county in Washington State then you face the possibility of an ignition interlock device requirement. This can arise at three different times following a DUI arrest. Depending on how the requirement is imposed a false positive can lead to a revocation of release, increased bail, or even jail as a sanction.

If an ignition interlock device is in your case you need to be very careful before you blow into. If in doubt about what you ate, or drank it is always best to rinse your mouth out with water and wait at least 15-20 minutes prior to giving a test.

About the author: Matthew Leyba is a practicing DUI Attorney in Seattle. He practices criminal defense with an emphasis on DUI and other traffic related offenses.